ETH Zurich and IBM Rüschlikon announced on May 6th that Aquasar is operational. Aquasar is an HPC system developed together by the two institutions using water to directly cool the integrated circuits. The water with a temperature of about 60 oC is used to heat the building of ETH Zurich. The goal of this research project is to reduce the energy footprint of computing systems: It is assumed that computers use about 5 to 10% of the electricity worldwide.